IslandRoadster
Former Owner of #609
Is that any easier to reach than the right-front-fender mount? Looks like it’s blocked by the PEM and fender.
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Replacing the 12V aux Battery
- Thread starter scotty2541
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- Roadster
Is that any easier to reach than the right-front-fender mount? Looks like it’s blocked by the PEM and fender.
Hi CoolVariable,
Thank you for the pictures.
I am afraid I cannot help with that one.
It's an aftermarket stereo install and I am not familiar with it.
Sorry,
Shawn
Thank you for the pictures.
I am afraid I cannot help with that one.
It's an aftermarket stereo install and I am not familiar with it.
Sorry,
Shawn
You have to remove the wheel and the front wheel well panel. That is where the stock subwoofer would have been located.
Thank you, ML. How are you?
I will probably just have Javier do it, since he is installing my new brakes.
It's funny how this post has aged over the years. I fitted the Shorai LFX19 battery in 2015 and have had zero issues. I sold the car January and the new owner reports it's still had no issues even today. Cracks me up that there are people out there relocating the battery so it's easier to change rather than just fitting a better battery in the first place. Happy to take this result as I'm now going through the same mod on my Twizy and probably on the Model 3 also and getting the same skepticism from everyone. Lol
n2mb_racing
Active Member
Sounds pretty good. Have you found a Shorai that's a good replacement for the Model 3 battery?
The only thing I haven't seen answered is how any of the 12V lifepo batteries handle cold weather charging. Do any of them have built in heating elements to warm the battery before allowing charging? Otherwise, I could see how you could be stranded if you park the car in below freezing weather. The BMS in the lifepo would have to prevent charging below freezing, which means eventually it would run out of 12V power and the car would shut down.
Just found one of these batteries should solve that problem:
Cold Weather Lithium Deep Cycle Battery | RELiON
The RB20-LT is a cold weather performance lithium battery that can safely charge at temperatures down to -20°C (-4°F). This 12V 20Ah battery is ideal for small solar applications, LED lighting and more.
relionbattery.com
Ohmmu also makes a drop in Model 3 battery, but unclear if it has a heater.
12V Lithium Battery for TESLA Model 3
Battery Terminals: SAE, Positive Top Back LeftDimensions: 185mm x 116mm x 198mm (L x W x H) / +20mm for postsWeight: 9 lbsWhat's Included: 12V LFP Battery, Warranty Card ATTENTION: Please note that your vehicle may prematurely recommend 12V battery replacements when a LiFePO4 battery is...
www.ohmmu.com
Survived -20 outside this year with no issues. The battery comes with a lot of insulation material and it’s tucked away. Not sure about a model 3 but I’m glad I swapped over.
Based on my earlier testing, a couple of notes regarding the use of LiFePO4 (or similar) batteries in the Roadster (including a puzzle...).Sounds pretty good. Have you found a Shorai that's a good replacement for the Model 3 battery?
The only thing I haven't seen answered is how any of the 12V lifepo batteries handle cold weather charging. Do any of them have built in heating elements to warm the battery before allowing charging? Otherwise, I could see how you could be stranded if you park the car in below freezing weather. The BMS in the lifepo would have to prevent charging below freezing, which means eventually it would run out of 12V power and the car would shut down.
Just found one of these batteries should solve that problem:
Cold Weather Lithium Deep Cycle Battery | RELiON
The RB20-LT is a cold weather performance lithium battery that can safely charge at temperatures down to -20°C (-4°F). This 12V 20Ah battery is ideal for small solar applications, LED lighting and more.
Ohmmu also makes a drop in Model 3 battery, but unclear if it has a heater.
12V Lithium Battery for TESLA Model 3
Battery Terminals: SAE, Positive Top Back LeftDimensions: 185mm x 116mm x 198mm (L x W x H) / +20mm for postsWeight: 9 lbsWhat's Included: 12V LFP Battery, Warranty Card ATTENTION: Please note that your vehicle may prematurely recommend 12V battery replacements when a LiFePO4 battery is...
The Roadster (specifically, the 2.x versions) keep a 13.8v trickle charge (less than an amp) going to the battery whenever the car is asleep. There is a DC-DC inverter in the ESS that provides this power. When the car is awake, that charging is switched to a higher power (a few amps), but still at 13.8v. So, this is very different than the more modern Tesla cars, where those cars depend on the 12v battery to keep the base systems running while the car sleeps. In the 2.x Roadster, the only time the 12v battery is "used" under normal conditions is for a few seconds after the "Unlock" button is pressed on the key fob. At that time the battery is put under a brief 10+ amp load, which I suspect is just a system test to be sure the battery can provide power in the event of a major power system fault. This is what generates the "12v battery service required" VDS alert.
So, the puzzle. In my testing, I never saw the voltage going to the 12v battery ever exceed 13.8v. The specifications for charging the LiFePO4 batteries require at least 14.2v for charging to occur, and 14.4 for balancing the cells. How are these batteries ever charged?
I rode an ebike thousands of miles with a lot of charge cycles, I had Nissan Leaf batteries, no BMS just bulk charged. When I got done cell logs to start charging them better I found they were still perfectly balanced. So the real question is do these low power batteries need balancing. I don’t have an answer because now I’m balancing obsessed.
n2mb_racing
Active Member
Lifepo doesn't need to charge above 14 volts. There's very little additional capacity above 14 volts, so for cell life it is better to not charge that high. 13.8V would be fine. As long as you can get the BMS to balance the cells, 13.8 is a fine full charge voltage.
n2mb_racing
Active Member
Nice. Although, I think on the model 3 this might be as much of a big deal as it was on the Model S. The AGM battery is warrantied for 4 years and Tesla seems to have improved their charging / discharging to the point where the batteries aren't wearing out all that fast. The AGM battery on the model 3 is easy to replace and it looks like it only costs $150, vs $440 for the Ohmmu... It would have to last 12 years probably to break even. I think I'll probably just stick with the AGM battery. Plus, the new Model S has a lithium ion 12V battery now, so presumably the 3 and Y will get that soon. I'll probably sell my model 3 before I ever need to replace the AGM (knock on wood).
I was just going by what the manufacturer specified, both the charge voltage and what is necessary for balancing. 13.8v meets neither of those requirements. I also remember reading some time ago (likely a different manufacturer) that their BMS won't actually go into charge mode until the applied voltage is above 14.1 or thereabouts. A good match for an alternator-based vehicle; not so good here. Note this is different than an SLA battery, where the external charger is directly connected to the cells.
All that said, perhaps these guys do something different? As long as the battery can pass the few-second, 15 amp load test whenever the unlock button is pressed, the car will never complain regardless how much (or little) energy is actually stored in the battery.
smorgasbord
Active Member
I don't yet need another 12v battery, but I came across these. Anyone know if one of these lithium replacements would be suitable for a v2.5 Roadster?
Or, should I just continue to stick with AGM style lead-acid batteries? I think I'm on my second after 11 years. I know from experience that the Roadster works just fine with NO battery even connected, as Tesla Service did that once accidentally. I was able to unlock the car by opening the charge port door and waiting a few seconds. Hey, maybe that's a theft deterrent? /s
Or, should I just continue to stick with AGM style lead-acid batteries? I think I'm on my second after 11 years. I know from experience that the Roadster works just fine with NO battery even connected, as Tesla Service did that once accidentally. I was able to unlock the car by opening the charge port door and waiting a few seconds. Hey, maybe that's a theft deterrent? /s
n2mb_racing
Active Member
Those look good. Just need to find the right size. And confirm how it handles low temp charging. If you live in a really cold place, the 12v might not charge, leaving you stuck.
IslandRoadster
Former Owner of #609
For Lion batteries, typically you cannot charge them below freezing (32F/0C). You can discharge them, but not charge. If you're in a warm climate, no worries. But if you'll be driving it below freezing, you'll want to wire a heating mat to warm the battery up for charging. The link you sent states that the battery has a battery management system the doesn't allow charging in "extreme cold."
smorgasbord
Active Member
Looking at sizes, the YTX9-BS is, I think, the standard size for V2+ Roadsters. Those are 5.9" Long, 3.4" Wide & 4.2" with Positive on left, Negative on right.
Noco says this model is the right replacement. Data Sheet says charging temp supported down to -10ºC. But, sheet also says the battery is only 3Amp-Hours of capacity, a lot less than the 8Amp-Hours for the YTX9-BS lead acid variety. Problem?
Noco says this model is the right replacement. Data Sheet says charging temp supported down to -10ºC. But, sheet also says the battery is only 3Amp-Hours of capacity, a lot less than the 8Amp-Hours for the YTX9-BS lead acid variety. Problem?
Probably not a problem under normal circumstances. The battery is intended to be used under decidedly not normal conditions, where the car has a complete failure of the ESS. It, then, powers the flasher lights and such.
Under normal circumstances, the battery sits at its "float" voltage, specifically the 13.8v float for a SLA / AGM type battery. That's also the charging voltage, i.e. the car does not run the battery through a full charging profile, so a Lithium-based battery will end up a bit undercharged.
Under normal circumstances, the only time the battery is actually used is what appears to be a verification test whenever the Unlock button on the key fob is pressed. If the battery is there for emergency purposes, it'd be nice to know it's ok, right? Whether the car is locked or not, that Unlock press causes a few-second load test of something like 15 amps to be placed on the battery. As long as the voltage doesn't drop too far, the test passes. If it fails, you get the "replace 12v battery" alert on the VDS. Available charging current fairly low at an amp or so while the car is on, and changes to a trickle charge when the car is asleep, maintaining that 13.8v float. Basically, the battery sits there at 13.8v 24/7/365.25, awake or asleep, except for those few seconds of terror when it is tested.
Lithium based batteries tend to be really good at supplying high currents for short periods of time, so it's unlikely to fail the test, and if I'm reading the spec sheet right, it will have no problem with the 15+ amps doing any damage to the cells. The only thing I'd be concerned about is whether the battery's internal BMS will be able to keep the cells balanced without the battery ever seeing a full 14.6v charging voltage. If they get too far out of balance, you could see one of the cells open up with no warning as a consequence of that load test.
If it helps, I replaced mine last year with a regular SLA /AGM battery. If you're careful, it can be done without removing the wheel or jacking up the car. See 12v battery time (sigh)
My roadster is coming out of winter storage with snow hopefully over for
the year in the Ottawa, Canada. I started seeing an alert message regarding the 12v battery. I’m thinking it might be time to change to a lithium replacement. This is the one I have in mind that I understand is already used in the community: http://et.baysideperformance.ca/sho...h3utAKRIjhog5zH4yl3GehWwrC2DT51YaAltdEALw_wcB
And I forgot to add if that’s even relevant: my car is all year round in a garage that is not insulated. Temperatures probably range from -30 C to +30 C.
One last question (sorry if it’s a stupid question, I couldn’t find the answer from this thread): is there anything I need to disconnect before disconnecting the 12v battery? And then once the new battery is connected?
Any help is appreciated.
Thanks
And I forgot to add if that’s even relevant: my car is all year round in a garage that is not insulated. Temperatures probably range from -30 C to +30 C.
One last question (sorry if it’s a stupid question, I couldn’t find the answer from this thread): is there anything I need to disconnect before disconnecting the 12v battery? And then once the new battery is connected?
Any help is appreciated.
Thanks
-30C ambient will likely be a problem with the Lithium-based batteries. Most don't like to be below freezing (0C); check the specs before venturing down that path. Lead-based batteries are much more robust in that regard, also a lot cheaper.
Also, I'd be careful in checking what the battery's BMS requires in terms of charging voltage. The car really is designed to "manage" a lead-based battery, doing so in a very simplistic manner. It's a relatively easy swap, one I have done without even removing the wheel.
Also, I'd be careful in checking what the battery's BMS requires in terms of charging voltage. The car really is designed to "manage" a lead-based battery, doing so in a very simplistic manner. It's a relatively easy swap, one I have done without even removing the wheel.
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